Question

I’m making a basic game in openGL with GLUT, and I’ve come across a small hitch.

When I attempt to draw an object from a class into my world, it gives everything a tint of colour which was last created with the function makeMaterial (see below).

Does anyone know how I could restrict these changes to being applied to the object only?
I’ve tried push/pop, but it doesn’t seem to limit anything.
Additionally, if the last colour drawn is black, I see nothing at all, except for my snowman.

Here are the relevant code:

makeMaterial :-

makeMaterial( float r,float g,float b,float a,float s )  
{   
    float color[4];  
    float white[4]; 
    GLfloat surfshine[1] ; 
    surfshine[0]=s*128.0 ; 
    color[0]=r;color[1]=g;color[2]=b;color[3]=a;  
    white[0]=0.5;white[1]=0.5;white[2]=0.5;white[3]=1.0;   
    glMaterialfv(GL_FRONT_AND_BACK, GL_AMBIENT,color);  
    glMaterialfv(GL_FRONT_AND_BACK, GL_DIFFUSE,color);  
    glMaterialfv(GL_FRONT_AND_BACK, GL_SPECULAR,white); 
    glMaterialfv(GL_FRONT_AND_BACK, GL_SHININESS,surfshine); 
} 

makeMaterial in use :-

makeMaterial(0.05f,0.05f,0.05f,1.00f, 0.4f);
glPushMatrix(); 
glutSolidCube(10.0); 
glPopMatrix(); 

my draw function :-

void drawToScene(void) {    
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT); 
    glLoadIdentity();   
    uniformFPS.setStartTime(glutGet(GLUT_ELAPSED_TIME));

    camera.updateCamera();
    lvl1.drawLevel();
    enemy.drawSnowman(350.0f,6.0f, 200.0f);
    crosshair.show();

    glutSwapBuffers();      
    uniformFPS.enforceChecks();
}

Answer 1

If you really want to ensure you are restricting changes to a specific section, you should be able to use glPushAttrib(GL_LIGHTING_BIT) before you do your makeMaterial call, and glPopAttrib after your drawing of the object is done. The reference for glPushAttrib here shows what properties are push’d by each of the possible bits you can supply. I don’t know that this is a particularly well regarded way to handle your state however.

A more general solution would be to make a call to makeMaterial with appropriate values before each set of drawing commands, i.e. assuming you have just one material for your snowman and one material for your world:

//...
makeMaterial(1.0f,1.0f,1.0f,1.0f,1.0f);
lvl1.drawLevel();
makeMaterial(0.5f,0.5f,0.5f,0.5f,0.5f);
enemy.drawSnowman(350.0f,6.0f,200.0f);
//...